Radio frequency tuned circuit and tube socket assembly



S. Y. WHITE RADIO FREQUENCY TUNED CIRCUIT Nov. 2l, 1950 AND TUBE SOCKET ASSEMBLY 2 Sheets-Sheet 1 Original Filed Dec. 8, 1942 ZIUNVENTOR.

@fm/T @"7 BY ATTORNEYS Nov. 2l, 1950 s. Y. WHITE 2,530,639

RADIO FREQUENCY TUNED CIRCUIT AND TUBE SOCKET ASSEMBLY Original Filed Dec. 8, 1942 2 Sheets-Sheet 2 f/q. lo. A "m 90 kiem f 2,0 my

ATTORNEYS Patented Nov. 21, 1950 RADIO FREQUENCY TUNED CIRCUIT AND TUBE SOCKET ASSEMBLY Sidney Y. White, Bayside, N. Y., assignor to Victor S. Johnson, Chicago, 11.; Victor S. Johnson, Jr., administrator de bonis non of said Victor S'. Johnson, deceased Continuation of forfeited application Serial No. 566,373, October 15, 1943, which is a division of application Serial No. 468,195, December 8 194i?, now Patent No. 2,451,643, datedv October 19, Serial No. 725,685'

'lihis application January 31, i947,

9' Claims. (Cl. Z50-16) This invention relates to radio apparatus, and is particularly, although not exclusively, concerned with mobile radio apparatus suitable for meeting the exacting requirements of military service on land, at sea, and in the air.

Such apparatus may becarried on a Wide Variety of vehicles such, for example, as a truck, a tank, or a naval airplane catapulted from a cruiser. It may be subjected, therefore, to -iolent shock and to extreme and protracted vibration. Again it may be carried on the back of a soldier.

Such apparatus may be used in every condition of climate and Weather to be found on the face of the earth, and in every season. It may be exposed to dust, mist, rain, sleet and snow from the air, and to mud and oil spray thrown up from roadways. It may be exposed to radical and' abrupt changes of temperature, humidity and' air pressure by being carried in the space of only a few minutes from a tropical desert into the substratosphere, or vice versa.

It is often desirable that many communication channels be made available, and that the distance at which a transmitter may be received shall be limited, in order that the same communication channelsV may be used in dierent regions without the possibility of mutual interference, andr alsoas a safeguard against listening in bythe enemy. For these reasons, among others, it is often desirable that apparatus for military use be' designed to operate in the ultrahigh frequencyrange. The ultra-high frequency range has important uses for non-military es Well as military purposes, but its use imposes severe requirements.

The nature of these requirements may be Well appreciated if the conditions met when tuning in a broadcast station on a home radio receiver are contrasted briefly with the conditions met in eli'ecti'ng communication between mobile units operating in the ultra-high frequency range.

The broadcast station is an elaborate and expensive, stationary installation, and is under the supervision of a staff of highly trained radio engineers. No pains or expense is spared to assure that the station ismaintained: precisely on the assigned frequency. The station is constantly on the air. The home set user can search for the station signal and can` adjust the tuning to the signal when he findsl it. The broadcast station, moreover, is allotted a 10' kc. channel which represents nearly one per cent of the entire standard broadcast band and approximately two-thirds per cent o1' the highest frequency at which any transmitter is operated in the standard broadcast band. Accuracy Within one per cent can be depended upon to bring the desired station. For such simple and coarse operation, the dial is a mere convenience; it is by no stretch of the imagination a precision instrumentality relied upon to show the exact frequency for which the home receiver is set.

In the ultra-high frequency military eld conditions are entirely different, the requirements being incomparably more severe. The transmitter is not constantly in operation, so that there is no signal to search for. Contact must be established through pre-setting the transmitter and the receiver to the precise frequency assigned. There can be no twiddling of dials at thev receiver. Where accuracy of tuning within one percent would sufice to bring in the standard broadcast station, a one percent error of tuning in the range of 15o mc. would constitute an error of 1500 ko; i. e., an error in excess of the entire standard broadcast frequency range, or enough to miss one hundred channels as there made available and fty more besides. The same degree of inaccuracy that is permissible in tuning a home set to bring in a broadcast station would miss a range wider than the entire standard broadcast band. The further point should not be overlooked that the transmitter in accordance with the present invention, as Well as the receiver, is generally a light, mobile unit, andy is subject to the same limitations the receiver. Since errors of the transmitter andL the receiver may be equal and cumulative, the receiver cannot be allotted a tolerance representing more than one-half of the permissible lack of correspondence of transmitter and receiver frequency, because a like tolerance must be accorded to the transmitter.

In addition to the foregoing, these mobile transmitters and receivers are required to operate under varying conditions of power supply. The source of' voltage may be a storage battery varying between 20 and 30 volts; and the line voltage for operating' A. C. transmitters and receivers may vary` between and T35 volts.

The crucial elements affecting the precision and the permanence of precision of receiver tuning and of transmitter tuning are found in, or in close association with, the ultra-high frequency circuits. In accordance with the present invention these elements are chosen of such materials. are constructed in such forms, and are associated and combined with one another into a head unit in such manner that the influence of tempera- 3 ture changes upon frequency is drastically and definitely limited, and that such slight changes of frequency with temperature as do occur are unalterahle, so that the initial limitation will be dependably maintained.

The electrical elements of the head unit are desirably mounted in an airtight housing in which they are rendered immune to dust, dirt and weather, and substantially free from changes of humidity and air pressure. The entire head structure is shock-insulated.

The head unit should desirably be capable of performing certainly and dependably without overhauling or readjustment for a period equal at least to the lives of the tubes; namely, 500 hours of actual service, or one year of service in elapsed time.

It is the primary object of the present invention to provide universal head units for incorporation in radio receivers and transmitters, ca- P pable of pre-set dial tuning with the precision reqm'red to establish communication in the ultrahigh frequency range, and capable of withstanding without detriment or permanent change, and even without temporary incapacity, the most severe conditions of every type of service, yet sufficiently light and compact to admit of incorporation in transmitters and receivers intended to be used in aircraft or to be carried into action on the backs of soldiers.

It is a further important object of the invention to provide head units of the kind referred to which can be produced in quantity with liberal and comfortable manufacturing tolerances for most of the parts, in some instances tolerances of as much as two per cent.

Quantitatively, the more important requirements to be met in service are roughly (l) that the head shall be capable of pre-set tuning with an accuracy within one 10 kc. channel at 150,000 kc.; (2) that it shall suffer no detriment from shocks of 8 gs., such as will be encountered in a tank or when an airplane carrying the unit is catapulted from a cruiser; (3) that it shall not be rendered inoperative nor temporarily incapacitated by vibration; (4) that it shall not be temporarily incapacitated nor permanently altered in its frequency characteristics by temperature Variations from 40 F. to +180" F.; (5) that it shall not be incapacitated by variations of atr mospheric humidity ranging from 5% t0 100%; (6) that it shall not be incapacitated by any air pressure variations to which aircraft are subject; and (7) that it shall not be permanently affected nor temporarily incapacitated by any combination of two or more of the conditions referred to under (2) to (6) inclusive.

Other objects and advantages will hereinafter appear.

This application is a continuation of my forfeited application Serial No. 506,373, filed October 15, 1943, for Radio Apparatus, which application was in turn a division of my pending application, Serial No. 468,195, filed December 8, 1942, now Patent No. 2,451,643, for Precision Radio Apparatus, the complete disclosure of which is made a part of this specification by reference. The present invention is directed primarily to features of a socket assembly and connections therefor including the combination of the socket assembly with a coil assembly which is adapted to be connected in circuit with the socket assembiy. Features disclosed but not claimed herein are disclosed and claimed in my parent application, Serial No. 468,195 and in other divi- 4 sional applications thereof; to wit, Serial No. 506,372, filed Oct. 15, 1943, now Patent No. 2,407,359, in the name of Sidney Y. White, for Radio Apparatus; Serial No. 506,374, filed October l5, 1943, now Patent No. 2,438,592, in the name oi Sidney Y. White for Electrical Condensers; Serial No. 506,375, filed October l5, 1943, now Patent No. 2,422,381, in the name of Sidney Y. White, for Method of Lining Up Unicontrolled Tuned Radio Apparatus; Serial No. 506,377, filed October 15, 1943, new 'Patent No. 2,407,360, for Method of Limiting Changes of Tuned Circuits in Response to Temperature Changes, in the name of Sidney Y. White; Serial No. 551,805, led

-1' August 30, 1944, now abandoned, for Electrical Condensers, in the name of Sidney Y. White; Serial No. 711,437, iiled November 21, 1046, now Patent No. 2,509,049, for Precision Radio Apparatus, in the name of Sidney Y. White; and Serial No. 711,438, filed November 21, 1946, now Patent No. 2,491,347 for Precision Radio Apparatus, in the name of Sidney Y. White.

Fig. 1 is a plan view of a coil assembly embodying features of the invention;

Fig. 2 is a rear end view showing the coil assembly of Fig. l together with an associated tank condenser;

Fig. 3 is a, View in side elevation of the coil and condenser assembly of Fig. 2;

Fig. 4 is a bottom view of the coil and condenser assembly shown in Fig. 2;

Fig. 5 is a longitudinal sectional view showing details of the condenser of Figs. 2 to 4, inclusive;

Fig. 6 is a sectional view, partly broken away intermediate its ends, of a condenser which may be advantageously employed in the transmitter and in the receiver;

Fig. 7 is a sectional View taken upon the line '1-1 of Fig. 6 looking in the direction of the arrows;

Fig. 8 is an end view of the oscillator assembly cooperating with the tuned circuit assembly of Figs. 1 to 4;

Fig. 9 is a view in elevation of the structure shown in Fig. 8 as seen from the left of Fig. 8;

Fig. 10 is a fragmentary View looking down on the structure of Figs. 8 and 9; and

Fig. 11 is a sectional view taken on the line Il-II of Fig. 8, looking in the direction of the arrows, and with the tube of Fig. 8 removed.

A practical embodiment of tuning structure applicable to the oscillator, R. F. amplifying, and mixer stages described in said parent application is illustrated in Figs. 8 to 11, inclusive, for example, for the oscillatory tuning assembly in which a vertical clamping plate 93 is secured to one side of the base block 90 by screw 98. This clamping plate is set into a recess of the base block, and extends upward alongside the adjacent vertical Wall of the block to a level a short distance above upper coplanar horizontal end faces of said walls. A rabbet is thus formed by the upper end of the clamping plate 96 which extends above the adjacent wall of the base block 90 and by the upper horizontal face of said base block wall. A corresponding opposed rabbet |00 is formed at the same level in the opposite wall of the base block, so that the base plates of supporting units for tuned circuit assemblies as illustrated in Figs. 1 to 4 may be set in the rabbets and clamped in place by the plate 96, with the hollow cylindrical coil forms accurately aligned in coaxial relation with one another.

The plate 96 will be seen to cooperate with the base block 9u to. form a o-clamp.v The opposed jaws of the clamp extend parallel to. one. another and yparallel to the axis: of the channel in the block' 9|); The. base plates; of the tuned circuit. assemblies; may, therefore, be set and clamped in diierentA selectedI positions; longitudinally of the block 90.. Thev plate 96. comprises an anchoring. portion` screwed into firm and unv-arying electrical contacty with the block 99 and a, bendable portion extending therefrom which is always spaced from the. block 98 throughout its: entire length, so that circulatingcurrents; induced in the. clamping structure, are; provided with an un,- varying and unambiguous current path.

A core lia: is mounted uponV ay ceramic thrusty rod lll. for cooperating with the windingv ci the oscillator assembly in. xedposition longitudinally oi the rod for controlling the. tuning ofV the oscillator circuit in accordance with the long-itudinal movement of the thrust rod.

As. disclosed in the"l parent application, the rod llt preferably operates in the same manner the severalV tuning; cores ci the transmitter or receiver to provide a. iixcd relationship between the, tuned frequencies of the circuit assemblies and yfor gang tuningby a single tuning means.

Figs. 1 to 4. inclusive, disclose desirablel forms. of tuned circuit assemblies and'parts thereof.. each. employing a cylindrical. coil form and. a solenoidal coil. woundy thereon.

Referring; to Figs. 1,A 2 and 4 the means for supporting the coil 35 and its associated condenser is shown as: comprising a generally rec.- tangular shaped plate. |65 molded of ceramic insulation material and having formed therein threey cylindrical holes- |61V and a pair of' elongated slots |68. Centrally of the block at its frontand.` rear'iti is provided with arcuate. shaped. portions |19 from which depend short tapered tongues and between the arcuate portions lll)y the. middle portion of the plate is undercut in anl art-:natev shape as indicated at |12. The entire. plate is finishedl to the shape' shown bya molding operation and is; then baked at a high temperature.v

The coil supporting torni liliv is shown as coinprising a generally cylindrical shaped tube composed. oi the same ceramicl material of which the plate; |65 is formed. The coil form has a spiral shaped groove LM form-ed therein adapted to accommodate the: coil 35 which is herein shown as. comprising a thin metallic ribbon |115 of two turns, which maybe heated when applied to the coil form, so that it may develop tension. through shrinkage as it cools'. The. coil form is also longitudinally slotted as at4 |116; the slot being tapered to: accommodate the tongues; |.'|L|( so that the slot If'llS. and tongues Ill. provide means. for locating the. coil form in a definitey position on the supporting plate |665.A A material which, will glaze is` applied tothe portions; ofk the` coil form andy plate |525 which are to be brought into4 contact with each other and. the members then: baked to glaze the material which thereupon unites the supporting blocks: and1 coil formv into a unitary rigid stableV assembly. The ceramic material is preferably of such a nature that its surface conta-ins a large number of small particles which project beyond the general surface level and puncture theskin of the ribbon in numerous places, thereby' entirely preventing any slippage ci the ribbon on the coilA form. The result isv that the coil is. maintained tightly in engagement with the coil form at all times and does not change in shape due to any f. terial' (see Figs. 3 and 5).

changes in temperature or humidity; In other Words, the` coil and coil form are., as it were, locked together throughout the full length of the coil and the size and shape of the coil remain at all times the same, as those ofv the coil form. This arrangement obviates any non-cyclic variation in distance between one turn. of the coil and another and also. any non-cyclic variations in the diameter of the coil so that once the coil is wound, its inductance. thereafter is not subject to non-cyclic variations due to temperature or aging. semi-elastic material such as sterling silver. Such material combines with high conductivity a softness permitting ready penetration by the coil' form crystals and an elasticity capable or maintaining the` required tension. Pure silver has been found unsuitable because it does not have` the required elasticity.

Referring to Figs. 1 to. 4, the powdered iron slug l5 is secured against the lower surface of the block |66 by means of a pair of screws Il? which pass through the slots |53. The inner face |18 of the slug l5 is arcuate in shape so that it may be moved. inwardly into engagement with the surface of the. coil form The slug l5 may be adjusted' for controlling the slope of the tuning curve of the oscillator. The left-hand end of the ribbon |15 is. soldered to an inwardly extending tongue Eli! formed on a metallic coil erminal |89' which has a flat portion itil held against the lower face of the plate I by a threaded hexagon head screw: |32; The width of the tongue |19 is substantially equal to that of the groove |14 in the coil forni so that it engages the sides of the groove and thereby prevents the coil terminal Hillfrom rotating when the screw |82 is tightened up. Coil terminal |80. is also provided' with a depending lug |53 whose lower edge is provided with an. arcuate surface Fig. 2, adapted to engage and to be soldered to a metallic cylindrical coating or thin sleeve |185 secured. to the outer peripheral surface at one end of a. thin tube |85 formed oi insulating ma- A similar but somewhat smaller metallic coating or sleeve i8? is provided near the other end oi tube E85 and the interior of, the tube is provided with a thin metallic coating or sleeve |88, so that the entire unit forms an electrical condenser.

The coil terminal |39r fory the other end of the coil is similarin construction to coil terminal |83, except that its parts are reversed, and corresponding parts of the two terminals are designate-d by the same referencev numerals. rShe tongue. |79 of terminal |39 is secured and soldered to the other end of the ribbon |'f5- and the arcuatev surface |84 of its depending lug |33: is. in engagement with and soldered to the coating |81 of the condenser. The mid-tap 53 (Fig. 3) of the; coil is soldered to a tongue le?, formedon the center terminal. |95 whose main body portion. is flat and is threaded to receive the secu-ring screw |1972'. |lhe tongue its extends substantial-ly ther full width of the spiral groove in thev coil form, thus.. preventing rotation. of coil tap. isi when the screw |92. is tightened. rlhe upper ends ot the hexagon securing screws 32 and |92 are rounded ofi as indicated in Fig. 3 at |93, thereby providing switch contacts for the coil and condenser assembly. lt will be noted that the condenser 66 described is. connected. across. the ends oi the oscillator coil Se.

In the illustrative tuned circuit assemblies described, a ribbon having a thickness. of about The. ribbon of the coil is dcsirably a.

three mils and a width of fifty to seventy mils may be advantageously employed. These dimensions are cited by way of example, however, and not as defining practical limits.

A construction suitable for a small condenser of stable capacity corresponding to any one of the condensers 46, 41 of Fig. 8 is shown in Figs. 6 and '7 in which the condenser is shown as comprising a cup-shaped member ZIB formed of ceramic material and whose interior surface is coated with a thin coating 2 I'I of silver, the hole in the ceramic material then being filled up by a plug ZIB of lead whose top surface ZIB is disposed slightly above the level of the top 22D of the ceramic body. The plug 'M5 at its center is provided with a threaded hole 221 adapted to receive a threaded screw 222. The major portion of the outer surface of the ceramic body is covered with a thin layer 223 of silver, the silver layers 2H and 223 being in intimate contact with the ceramic material. A hollow cap 224 composed of non-corrosive metal is then placed over the silver coating 223 so as to be in rm contact therewith. The top portion of the ceramic body is provided with an outwardly extending iiange portion 225, thereby providing a long dielectric surface path between the top of the silver coatings 2li and 223 which alone determine the capacity of the condenser. It will be obvious that there is no slippage between the ceramic material and the condenser coatings 2H and 223 due to temperature variations which might affect the capacity of the condenser, any slight slippage between the lead plug and silver coating 2i?, or between the metal cap 22!! and silver coating 223 having no effect on the capacity of the condenser. The screw 222 may be inserted through a hole in a shelf or supporting bracket and then screwed into the plug 2I8, thus providing a ready means for supporting the condenser. At the same time the screw provides means for electrically connecting one side of the condenser to a terminal of a. circuit, the screw 222 passing through a hole in the terminal so that when the screw 222 is tightened up the lower face of the terminal will be drawn into firm engagement with the upper surface 2li) of the plug 2 i8. The upper surface 225 of the screw also may be utilized as a switch contact to connect the condenser to a circuit while the lower flat surface 221 of cap 222 may be used as a switch contact to connect the condenser to another point in the circuit.

At 125 mc., if we use concentrated circuit elements of the L-C type, the coil used can be little more than 2 inches of wire. We can, therefore, use no leads whatsoever, in a disciplined circuit, as we want all the wire possible on the coil obeying a single set of rules of expansion and vibration.

Since such high sustained accuracy is sought for, no structure or material can be used except of the most unchanging nature. Physically, glass, quartz and ceramic are most suitable and have good retrace characteristics of dielectric constant and physical size when varied with temperature. No structure can be employed where there is the slightest possibility of any permanent change to any degree, either electrical or mechanical.

The type of tuning employed is of the core type, and while ferrous cores are advantageous for many purposes, the conductive type core, as for instance silver or copper, may well be used in some applications.

The tuned circuit must, therefore, be designed with the requirements of core tuning in mind. It is basic, however, that before we can tune the circuit over a range, the circuit without such tuning means must in itself maintain a fixed frequency to a high order of accuracy. It must also allow trimming, tracking and aligning with a precalibrated dial having great length and accuracy of presetting. It must have no wiring at all.

The coil design must allow use of one to four turns, for example. It must allow bringing out a tap to any turn or fraction of a turn. Its external tuned circuit must include a tuning condenser having minimum inductance, and the whole outside return loop must be minimized.

The concentration of over of the inductance is actually in the coils of the tuned circuit assemblies described where it is capable of being acted on by a core.

The diameter of the coil is chosen to be about 405 mils in the present instance for use with a. 375 mil core. Considerable difficulty is had in the ceramic art in making thin walled tubes beyond a certain minimum thickness of wall. Maximum tuning ranges obtainable with core tuning are reached where the core substantially fills up the coil, but it must still freely pass through the bore of the coil form. If we chose this same ratio with a mil core, the wall thickness would be less than 5 mils, an impracticable iigure for quantity production in the present state of the ceramic art.

The coil form is made with grooves for the conductor. The thick lands support the thin grooved portion, a point of particular importance during firing. The lands also guide the conductor during the winding of it.

Since the conductor chosen must have high conductivity, its thermal coefficient of expansion must also be high, at least two or three times that of the coil form. A spiral winding inherently has no strength of its own, so it must be the mechanical slave of the coil form. This means the wire must be wound under sucient tension and have enough elasticity to cling to the form at the most adverse temperature.

The cross-section of the conductor is a very thin strap, rather wide. If large, round conductors are used, such as #'14 round wire, the current tends to hug the coil form as it is the smallest diameter of the turn. Any good conductor has a large temperature coefficient of resistance, however, and if the temperature be raised the resulting increased resistance causes a redistribution of the current, causing the diameter of the mean current path 'to be increased. This markedly increases the inductance, since diameter of the current path is squared in the formula for the inductance coil, and great changes in frequency result.

By using a very thin strap of the order of three mils in thickness, this effect is minimized and a disciplined current path results. Instead of using pure silver, sterling silver is used for greater toughness and elasticity and may be wound on the form quite hot by passing a heavy current through it while winding, in which case it shrinks on the form. Tension may be used also, suicient to stress it nearly half way to its elastic limit so it hugs the coil form like a rubber band.

Silver plated Invar or Nilvar used in large cross-section maintains its cross-section under temperature variation, but the current redistribution is the same as for pure silver, and it must be wound under tension and in general has no .advantage over the ith-in sterling 'silver strap, which may be flattened wire.

It is of great 'advantage to use .ceramics :of the low .loss type fsuch as Al Si Mag 196 because of the presence on the surface of minute sharp crystal structures which apparently pierce the skin of .any unhardened metal pressed firmly against them. Repeated temperature cycling of 'these coils from -40 to +217 F. show no creepage Iof the winding, since each unit length is captured by its adjacent crystals and held -rmly in place.

The length .of coi-l chosen must also depend in partv upon the tun-ing curve desired and upon the length oi core travel most easily obtained with a desirable dial mechanism. A coil 375 mils long, measured center of winding strap to cen-ter of winding strap gives an active core movement of about 250 mils for 25% tuning range.

In any coil to be with a core the inside of the coil form must be left free to pass the core. Most Ameti-leds of terminating coils use rivets, eyelets, or passing the conductor through holes in the foi-m, all of which would interfere core movement. Some structure out-side the simple cylindrical coil form is, therefore, relquired. This takes the form of the plate or bie-cl: its `with its asseciated terminal .blocks wie, its and t9! (see Figs. 2, 3 and 4).

The block i555 is preferably glazed te the coil for-m. Plastic oements are undesirable because ci cold flow and change with age, but a goed glaze in the icint fired at 1700" really makes the two pieces unitary.

Plate it .allows use of massive structures such as `blocks |89 and lf3@ to be employed to give a rigid and defi-nite termination of the nductance at either end. These blocks are given large crosssection so that -they will have a minimum possible :induct-ance, and the tongues |19 provide exact termination of the inductance woundlon the form, in that the talee-oil of the current is normal to the axis :o'f the coil. Each `tongue |19, being the full width oi groove |14, provides a rigid non-turning structure when the contact screws .|82 are tightened. `Shaping of these blocks `to include .the turned up portion |83 (Fig. 3) provides a .conductive holder for a cylindrical condenser to `be used :for tuning the circuit.

A number of assemblies have been assembled and tested using the condenser .60 of Fig. 5, which isa commercial form where the `capacity may be formed between the inner plate E38 .and the two bands |85 and .|85 forming two condensers in .series, or the outerband |85 may be lcontinued around the end of the hollow cylinder joining the inside plate `|88 forming a single .condenser through the ceramic body |86.

When :this condenser is laid in the cradle formed by the connecting blocks |83 it will be seen that an absolute minimum ind-uctance return path closing the physical separation between the ends of the coil proper has vbeen achieved.

It is found to be a considerable advantage .in this self-contained structure that rounded contacts |33 can be used as a switch in the case ,of multi-band apparatus. There is a `real ,problem insw-i-tching uitra-higlfi irequency circuits where the switch is placed within the tuned circuit. A coil in the `broadcast band may easily Vhave an R. F. resistance of ohms, lor 5000 milliohrns. A satisfactory .commercial type of small switchmay have contact resistances of to 4c millio-hrns., which is negligible in proportion to 50.00 milliohms. A two-turn coil such as shown `in Fig. 14, however, may have a total R. F. resistance 'T0 in the entire tuned circuit of only v#i0 milliohnis, and consequently the contact resistance of any practical livform of switch, which of Ynecessity must besrnall because of the small physical dimensions or" these circuits, becomes a -substantialportion of the total resistance. It is an adv-antageousv feature of the present invention that each coil carries its own tank condenser with it, allowing switching of the charging ycurrent to the electrodes c-f the tubes only, a ich easier matter.

Provision of these contacts also allows" desir' able slipping of the whole tuned circuit assembly Provision ci' the plate |66 also allows for `the ci la solid block trimmer |5 as shown Fig. 2. w

Plate .its also provides a #fastening means ifor the assembly as shown in cross-section 'in the csoifllaton Fig. 8. As mentioned previously, the ultra-high frequency cera-mics used have the sur' face property of sharp crystal structures which are able to pierce the sli-in of any reasonably soft Ametal by simple pressure. Advantage is taken ci that fact by having the tuned circuit assembly holder 9S, 9S form a C clamp. The clamp shown, when fully tightened, gives a surprising result, Iin that the entire set may be lifted by the tuned circuit assembly with absolutely shift in the position of the tunedecircuit assembly. By loosening screws l9.8, however, the tuned circuit assembly @t may 'be `readily slid baci; ici-th axially while maintaining strict alignment between the bore of the coi-l form and a -core surrounded thereby. It has been found that tightening up the screw 98 aga-in lcauses n0 shift in the position of the tuned circuit assembly and provides a positive lock against shitting due to any shock -or vibration or thermal working.

The necessary provision for a tap on the coil is met by the provision -oi the third contact S52 (Fig. 3), the block -|9|, and the tongue |36 engaging the coi-l.

In a practical receiver using this type of gear, the problem -of injecting the oscillator voltage into the mixer circuit is accomplished by coaxial mounting of the two assemblies, a distance between them being chosen to give the desired amount of oscillator injection into the mixer grid circuit, for instance.

Tracking between the voscillator and R. F. circuits may be accomplished by any one of several means, for example, by Aselection of the diameters of the `zcores for tuning `the circuits. One circuit tunes over a greater percentage range than the `other circuit, dep-ending on whether the oscillator is run at a -higher or lower .frequency than `the signal. rThe .ratio o'f the 'two diameters of the cores is a function of the frequency separation `desired to give the necessary intermediate frequency, which may Well 'be chosen anywhere between one megacycle .and twenty megacycles.

The tuned circuit assembly .shown Figs. .1 to 4 makes provision for a single unit that 4has in effect fastening means, tuning means, switch, tank condenser., trimming, tracking and aligning means in a single simple structure, so thatlall the frequency determining Aelements are well within a cubic inch, and under temperature, vibration 4and shock, `all travel together. rhere is no influence of the chassis upon the frequency. Ther-e is thus provided a `single universal unit that can .be used for transmitter, receiver, wave trap, or any of the numerous uses to which tuned circuits can be put.

The Q of these assemblies is found to -be quite "11 high without the core. If measured in air without any associated apparatus, the Q is about 700. When measured in the coil holder and with an oscillator tube assembly attached, as shown in Fig. 8, with the tube in place but not lit, the Q exceeds 400.

A further advantage of this type of construction is that no parasitic loops of any kind are formed to give resonant absorptive eifects or resonant voltage rises at any frequency within the operating range of the current acorn tubes, and in no case below 1500 mc.

The ultra-audion oscillator may advantageously be used, this being the simplest of all circuits. Elimination of the center tap might have been accomplished by shunt feeding the plate through a resistance. Such an arrangement is not considered most advantageous, however, because of the wattage dissipation and the voltage drop in such a resistor. Since it is desired to maintain the universality of application of this unit, it is often desirable to operate with such low plate voltages, as for instance in the battery type of acorns, that 20 volts drop in the plate shunt resistor' would force the use of a higher voltage battery.

An approximate center tap shown has an isolation resistor l associated with it, since with core tuning with the core introduced at one end, the null point (that point which is at zero potential to ground) shifts as the core is inserted. This shifting null is taken care of by the resistor, which prevents any substantial radio frequency energy from flowing down to ground through the plate energizing connection.

The ultra-audion circuit has the advantage that the cathode and heater are at ground potential, thus eliminating frequency uctuations introduced by way of the cathode to heater capacity, when the heater is energized from an alternating or fluctuating source of voltage.

It has been found that the capacity ratios between the electrodes of the acorn tube as now manufactured, both battery and 6 volt types, is very nearly ideal for this type of oscillator. assembly shown in Fig. 8, when operated from a power source which varies from 20 to 30 volts gave a total frequency shift of 7 kc. at 132,000 kc., with a tuning condenser of mmf.

The high potential portions of the circuit of Figs. 8-11 are the three connections 43, 5x6-4l and 56 on the end of the socket shown close to the tuned circuit assembly 34. No wiring whatsoever is used in this whole assembly, and consequently no resonant loops can be formed. The plate connection is directly to one end of the tuned circuit assembly 34 through a simple metallic contact 43. The other end of the tuned circuit assembly Sfl makes connection through a grid condenser 4l as shown in detail in Figs. 6 and 7. This grid condenser, which is also a nut for holding fast the terminal contact 221 on the socket 228, is armored with a silver cup 224 to stand the abrasion of its use as a switch contact,

and is also the holddown for the grid leak 49.

This condenser desirably has a value of 25 mmf.

The acorn socket 228 is that disclosed in U. S. Patent No. 2,290,306, granted to me on July 21, 1942. The socket 228 is mounted in this assembly so that a spring 229 forces it down against the switch contacts |82 and 192 of the tuned circuit assembly, but the socket has great lateral rigidity in its mounting. The center contact 56 is mounted on a blank hole in the socket 228, as shown, and must be resilient as shown (see Figs. 8, 9 and 10) since it is practicable to line up two The rigid contacts, but not three. The resistor El in the B lead and the grid leak 49 are of the type wherein colloidal carbon is baked onto a glass thread, and are almost free of capacity effects. Because. of their resistance, such resistors cannot form portions of resonant circuits. They are terminated in the condenser network shown which is a type of bypass condenser 2S, and lugs are brought out at the bottom to connect to the embedded resistors 5B, 58, 239 of the wire wound type shown in the assembly, thus acting as radio frequency chokes as well as resistors. The cathode and one side of the heater are connected to ground by a plate 23! pressed flat without insuiation against the bracket 95a, and the other end of the heater is brought out through a similar plate 23 isolated on either side with mica sheets, and brought back through the bracket 95a to pick up its appropriate resistor 239 buried in the bracket 95a. The outer plate 229 of this assembly is grounded through the mounting screws 232 and is made of heavy Phosphorbronze to form a spring of great strength to force down the socket onto the contacts of the tuned circuit assembly.

Capacitor 23 is of a type of construction found highly advantageous and desirable, and universally employed by me in the ultra-high frequency range, and consists of a sheet of metal separated from the body of the set by a sheet of mica, forming a built-in, non-inductive bypass to ground. This form of construction insures freedom from unwanted resonant circuit combinations formed by the wiring of the set and wherever a bypass condenser to ground is indicated in the drawing it is of this type. All leads have resistances in them to prevent formation of resonant loops. Resistances 50, 23D and 53 are of the wire wound type, being embedded in a grounded metallic block 95a (see Figs. 8 and 9) and act as radio frequency chokes to prevent radio frequency voltage from entering the supply leads.

The design of the resilient contact 56 must include a fundamental design requirement which can perhaps be more readily understood in connection with the C clamp jaw 96 of Figs. 8 and 10.

Where it is necessary to maintain the frequency of a tuned circuit to a very high degree of accuracy through wide ranges of temperature, it is necessary to avoid having one curved piece of metal tangent to another where the point of contact may be somewhat doubtful. Under' thermal stress wide variations in current paths can be expected in the currents induced in all such members surrounding tuned circuits. As shown in connection with 96, there is provided a denite line of contact held firmly by the screws 98, and a full clearance above that line of contact, so as the jaw 96 bows under the thermal stresses it oifers an unchanged current path to circulatlhg currents that may be induced into it.

Examination of Fig. 8 shows how the tuned circuit assembly 34 may be readily moved axially over a rather short distance such as a thirtysecond of an inch, to take up tolerances and allow alignment of the circuit with a pre-engraved dial. It can also be seen that coil holder and one associated oscillator tube assembly may be used at almost any desired frequency, say from 3 mc. to 600 mc. by inserting a complete tuned circuit assembly 34 having its inductance and capacity suitably chosen to operate in the portion of the spectrum desired.

In distributed capacities, an assembly of this 'nature is exceptionally low. All capacities, including the tube capacities, other than the tank condenser .663 itself, average about 3.8 mmf. A two-turn coil such as shown in Fig. 3, with the tank condenser omitted, will oscillate at 400 mc., showing that, when the tank condenser is inserted to bring its frequency down to an operating range in the neighborhood of 150 mc., We have a highly disciplined circuit of great stability.

The bracket e@ is shown in Fig. 8 as firmly screwed to the block 90, by screws 233, but may well be spot welded, if desired. The rst time after these assemblies are put together they have a rather large drift in frequency as they are given a thermal run, but the second run shows they have steadied down and reached the condition of mechanical equilibrium. In fact, thermal cycling beyond two times seems to be hardly necessary.

Frequency drift in the oscillator( assembly (Fig. 8) due to changes in temperature have been rather fully investigated and come under five main headings; the change in true inductance of the coil due to rearrangement of current path and expansion of the coil form; the change in the distributed capacity of the asscmbly due to use of ceramic in the tuned circuit assembly 3d and in the socket 22S which has a change in dielectric constant with temperature which is about 140 parts per million per degree; the temperature coefficient of the tuning condenser S; the temperature coefficient of the core material; and the change in relative positions between the core and the coil assembly due to the thermal coeriicient of expansion of the metals used in the dial mechanism. The grid leak :i9 has a marked coefficient of resistance variation with temperature, but its eiect on the frequency is found to be only one or two kilocycles at 150,000 kc. through the total operative temperature range. The grid condenser shown kis of the nominally zero temperature coeiiicient type and seems to have no effect with changes in temperature.

The true inductance of the coil Varies at a rate proportional to. the thermal coeflicient of expansion of the coil form which is six parts per million per degree.v Current redistribution due to the increased resistance of the winding conductor with heat is practically eliminated by the use of an extremely thin strap for the conductor.

The change in the capacity of the tuned circ uit assembly parts to each other through ceramic as a dielectric, as well as the change in capacity between the parts mounted on the socket 228, is of a rather high order, but since the total value of this capacity lies between l and 2 mmf., it, forms` a rather small part of the entire tuning capacity, being often of the order of 5% to 10% of such capacity.

Both the real and apparent inductance of the tuned, circuit assembly lower the frequency as the temperature increases. soa slightly negative temperature coeiiicient condenser 69- is used for tuningtheA circuit to provide a balance, result-- ing in very small change in frequency with temperature. These condensers employ generally available ceramic materials which. may: be chosen to yield a temperature coecient which is high ly negative, such asv an almost pure titanium dioxide mix,l which gives --750 partsk per million per degree, up to those going slightly positive inftheir temperature coeflicient of capacity.

Br-Oyision is desira'blyV made. for compensating'A i4' the effect of temperature upon the tuned circuit assemblies as herein disclosed. Disclosure of that feature is vmade in .my kPatent No. 2,451,643, out since disclosure of 'it is not necessary to an understanding of the invention claimed herein, no .showing nor `description of the feature herein is deemed necessary.

It is highly desirable that the core have almost no temperature coeiiicient of its own, as otherwise Yeither incomplete or very elaborate compensating means would have to be used. Cores of the ferrous oxide type, while having very low losses at `frequencies in excess of rnc., have marked temperature coefficients of both permeability and losses. Certain cores of the carbonyl rproduced type, however, are found to have a very high order of stability, both in regard to losses and permeability, when used at these frequencies. Great care is necessary in insulating and binding these spherical particles together, and particles must be chosen having differentiated internal structure, such as being formed of a plurality of concentric shells. The losses are markedly higher than those in the ferrous oxide type, but the cores are still decidedly usable. Total thermal drifts of l0 to 20 kc. at 106,000 kc. can be reproducibly obtained with this type core, when heated to several hundred degrees.

The dial .mechanism can be designed to maintain the relative positions of the coil and core throughout a wide range of temperatures as is described in my vcopending application, VSerial No. 464,812, filed November 6, 1942, now Patent No. 2,399,701, covering the dial mechanism.

I have described what I believe to be the best embodiments of my invention. I do not wish, however, to be confined to the embodiments shown, but what I desire to cover by Letters Patent is set forth in the appended claims.

I claim:

l. in a radio unit, in combination, a tuned circuit assembly comprising an insulating plate, a cylindrical coil form attached. to the plate, its axis disposed in parallelism with the body off the plate, a coil composed of 'thin metallic ribbon wound on the form, conductive terminal blocks on the plate and directly engaging the coil, and conductive screws passed through the plate and threaded into the respective terminal blocks, 'the heads of said screws being conductively connected with the coil through the associated'blocks and adapted to serve as terminal contacts, and a socket assembly comprising a tube socket in the form of a ilat plate of insulating' material, said assembly including contacts for the tube elements at radio frequency potential to ground, and means clamping said contacts to the socket and forming terminal contacts for engaging the cooperating terminal contacts of the circuit assembly, and a supporting framework through which the tuned circuit assembly and the socket assembly are mounted and maintained in cooperative relation to oneanother.

2. In a radio apparatus, in combination, an oscillator socket assembly for tuning by means of a tuning core .movable axially between predetermined limits of movement and for cooperation with a tuned circuit assembly, and a guiderway in which a tuned circuit assembly may be removably held and along which said assembly may be adjusted lengthwise of the path of core movement, said oscillator socket assembly comprising a tube socket in the form of a flat plate of insulating material, means for supporting the tube socket along one `edge with provision for asados@ rocking movement and for biasing the socket in a downward direction, but constructed and arranged to hold the socket rigidly against other movement, said assembly including at the margin remote from the supported edge contacts for separably engaging the tube elements at radio frequency potential to ground, said contacts being separably and slidably engagcable with corresponding med circuit assembly contacts, whereby diierent selected tuned circuit assemblies may inserted into cooperative relation to the socket assembly with corresponding contacts engaged, may then be adjusted longitudinally of the path o core movement and relative to the socket assembly while maintaining Contact engagement therewith, into a desired relation to the limits of core movement.

3. In a radio apparatus, in combination, a tube socket assembly ior tuning by means of a tuning core movable axially between predetermined limits of movement and for cooperation with a tuned circuit assembly, and a guideway in. which a tuned circuit assembly may be removably held and along which said assembly may be adjusted lengthwise of the path of core movement, said socket assembly comprising a tube socket in the form of a ilat plate of insulating material, means for supporting the tube socket and biasing it toward the tuned circuit assembly adjustment path, said supporting means being constructed and arranged to hold the socket rigidly against other movement, said assembly including contacts for separably engaging the tube elements at radio frequency potential to ground, said contacts being separably and slidably engageable with corresponding tuned circuit assembly contacts, whereby diiierent selected tuned circuit assemblies may be inserted into cooperative relation to the socket assembly with corresponding contacts engaged, and may then be adjusted longitudinally of the path of core movement and relative to the socket assembly while maintaining contact engagement therewith into a desired relation to the limits of core movement.

4. An oscillator socket assembly comprising, in combination, a tube socket in the form of a ilat plate oi insulating material, means for supporting the tube socket along one edge with provision for rocking movement and for biasing the socket in a downward direction, said supporting means being constructed and arranged to hold the socket rigidly against other movement, said assembly including at the margin remote from the supported edge, contacts for separably engaging the tube elements at radio frequency potential to ground, said contacts being separably and slidably engageable with corresponding tuning coil assembly contacts, whereby different tuning coil assemblies may be inserted into cooperative relation to the socket assembly with corresponding contacts engaged, and may then be adjusted axially of the coil and relative to the socket assembly while maintaining contact engagement therewith.

5. A tube socket assembly comprising, in combination, a tube socket in the form of a flat plate of insulating material, means supporting the tube socket along one edge with provision for rocking movement and for biasing the socket in a downward direction, said means holding the socket rigidly against other movement, said assembly including, at the margin remote from the supported edge, contacts for separably and slidably engaging the tube elements at radio frequency potential to ground, and means permanently associated with the socket for clamping said contacts to the socket, said clamping means forming terminal conductive switch contacts constructed and arranged to be slidably and separably engaged with, and pressed against, cooperating terminal contacts of separately supported, selected, tuned circuit assemblies under the biasing influence of the tube socket supporting means, one of the clamping means referred to including a condenser having an electrode in the form of a nut and a headed screw threaded therein.

6. In a radio unit, in combination, a tuned circuit assembly comprising an insulating plate, a cylindrical coii form attached to the plate, having its axis disposed in parallelism with the body of the plate, a coil composed of thin metallic ribbon wound on the form, conductive terminal blocks on the plate and directly engaging the coil, and conductive screws passed through the plate and threaded into the respective terminal blocks, the heads of said screws being conductively connected with the coil through the associated blocks and adapted to serve as terminal contacts, and a socket assembly comprising a tube socket, and conductors in said socket extended to provide terminals for engaging the cooperating terminal contacts of the tuned circuit assembly, and a supporting framework through which the tuned circuit assembly and the socket assembly are mounted and maintained in cooperative relation to one another.

7. In combination, a tuned circuit assembly including a coil, a condenser, and a plurality of spaced contacts, a socket assembly comprising a vacuum tube socket, conductors engageable with the tube terminals, said conductors themselves having extensions forming terminal contacts spaced to cooperate with the respective tuned circuit assembly contacts, and means for urging the contacts of the respective assemblies into engagement with one another, and a supporting framework upon which the tuned circuit assembly and the socket assembly are independently mounted with their contacts in mere bearing engagement with one another including means supporting the tuned circuit assembly for ready removal from the frame, the construction and arrangement being such that the tuned circuit assembly can be removed as a unit while leaving the socket assembly undisturbed.

8. In combination, a permeability tuned circuit assembly including a coil, a condenser, and a plurality or" spaced contacts, a socket assembly comprising a vacuum tube socket, conductors engageable with the tube terminals, said conductors themselves having extensions forming terminal contacts spaced to cooperate with the respective tuned circuit assembly contacts, and means for urging the contacts of the respective assemblies into engagement with one another, and a supporting framework upon which the tuned circuit assembly and the socket assembly are independently mounted with their contacts in mere bearing engagement with one another including means supporting the tuned circuit assembly for ready removal from theframe, the construction and arrangement being such that the tuned circuit assembly can be removed as a unit While leaving the socket assembly undisturbed.

9. In a radio unit, in combination a tuned circuit assembly unit comprising a coil and a plurality of spaced protruding contacts, a socket assembly comprising a tube socket in the form of a nat plate of insulating material, said assembly including contacts for the tube elements at radio REFERENCES CITED frequency potential to ground, means clamping said tube element contacts to the socket and lyhf clggrferens are of record m the forming protruding terminal contacts for engaging the protruding spaced contacts of the tuned 5 UNITED STATES PATENTS circuit assembly, and a supporting framework Numb r Na D t through Which the tuned circuit assembly and 2 0866631 H 1 me J I $22937 the socket assembly are mounted, the tuned cir- 2111397 Holmes "Mu 3715' i938 cuit assembly with capacity for adjustment 2135672 M0 mfs r' 8 1938 axially of the coil with the two sets of protruding l@ 2168351 L Og e tal' AOV 8' 1939 contacts in engagement with one another. 2212231 Gasselee a? "Aug'go 1940 SmNEY Y WHITE. 2,223,172 GGOI'ge NOV. 26, 1940 2,405,229 Mueller et al Aug. 6, 1946 

